Effect of thermomechanical treatment and tempering temperature on microstructure and tensile properties of India specific re duce d activation ferritic martensitic steel

In the present work, India specific reduced activation ferritic martensitic (INRAFM) steel was subjected to thermomechanical treatment (TMT) consisting of warm rolling at 973 K, followed by tempering for 90 min at two temperatures 1033 K and 1063 K, named as TMT1 and TMT2 conditions. Microstructural character-istics, hardness and tensile properties (at 300-873 K) of the INRAFM steel in TMT1 and TMT2 conditions are presented. INRAFM steel has shown significant improvement in hardness, tensile strength properties in TMT1 condition (i.e., tempered at 1033 K) compared to conventional normalizing and tempering due to microstructural refinement. However, tempering at higher temperature (1063 K) diminished the ben-eficial effects of TMT. The refinement in M23C6 and MX precipitates and ample improvement in their number density complemented by relatively high dislocation density (produced upon thermomechanical treatment) mainly contribute to the enhancement of elevated temperature strength of the steel tempered at 1033 K. On the other hand, the drop in strength of the steel tempered at 1063 K is attributed to the coarsening of M23C6 precipitates, annihilation and recovery of dislocation structure, with less number density of MX precipitates. Moreover, apart from enhancing the strength, the ductility of the steel has immensely improved in TMT1 condition. These promising results make TMT processed INRAFM steel a potential candidate material for nuclear fusion reactor applications.(c) 2022 Elsevier B.V. All rights reserved.